1. Field of the Invention
This invention relates to amplifier apparatus and, more particularly, to power amplifier output apparatus operating at radio frequencies.
2. Description of the Related Art
Electrical circuits which combine pairs of amplifier input signals supplied at the same impedance level, frequency and phase into an output signal at the same impedance level, frequency and phase are known in the art. Whether of the typical Branchline, Gysel or Wilkinson coupler configurations, these electrical circuits exhibit a 6 dB power loss (3 dB from the amplifier and 3 dB from the combiner) if one of the input signals is not present--for example, as a result of amplifier failure. Where the output signal developed is coupled to an antenna configuration in a cellular communications system, for instance, the end result is a decrease in coverage for the cell site, and a resultant inability for users to transmit to a Base Station in obtaining optimum phone service.